Macro Photography: Macro Images on a Budget
If you’ve a system camera then a macro lens is a wonderful thing to own. Macro lenses allow you to explore the world of the very small, revealing details that it’s hard to see with the human eye. However, macro lenses are relatively specialised, and with specialisation comes expense. You really have to want or need a macro lens to justify the outlay. Fortunately, there are alternatives to the macro lens. They don’t offer the image quality of a good macro lens but they’re a viable and inexpensive entry to macro photography. Part one today covers accessory lenses and reversing rings.
First however, a quick definition of what a macro lens actually is. Lots of zoom lenses offer a macro setting. If we’re being really pedantic these actually fall far short of being truly macro. A macro lens projects an image that is life-size onto a camera’s sensor. So, if your subject is 10mm across the image of the subject will also be 10mm when projected onto the sensor. A true macro lens is said to have a 1:1 magnification ratio (or 1x magnification) or higher. ‘Macro’ settings on zoom lenses are often only 1:4 (0.25x) or quarter life-size.
Accessory lenses (Diopters)
An accessory lens or Diopter is essentially a magnifying glass that fits to onto the filter thread of a standard lens. This adds a macro capability to a lens, without affecting exposure or metering. Unfortunately, of all the options discussed today and Wednesday, accessory lenses produce the lowest image quality. Add another piece of glass to an optics system and quality always drops. That’s not to say that accessory lenses are bad. They’re easy to use and are good fun. Accessory lenses can bought in different strengths, measured in dioptres. You can stack accessory lenses to increase the magnification but doing so really affects image quality and so isn’t recommended.
Here’s slightly odd fact: every lens you own is a macro lens. But only when it’s mounted onto your camera backwards (so that the front of the lens points into the camera). You can try this by carefully holding the lens backwards against the camera’s lens mount and shooting a picture. However, this isn’t a particularly convenient way to work. This is where the reversing ring comes in. It’s essentially a metal ring with a lens mount on one side and a screw thread on the other. You attach the reversing ring to the lens by threading it onto the lens’ filter ring (reversing rings are available with different sized threads, you buy the size that matches the filter thread size of the lens you want to use). The reversing ring is then mounted to the camera as though you were fitting a normal lens.
Unfortunately there is one big downside to reversing rings. They don’t carry a signal from the lens to the camera so functions such as autofocus and automatic metering don’t work. Worse still, you can’t alter the aperture unless the lens has a manual aperture ring. For this reason I use an old (and very inexpensive) Minolata manual focus lens found on eBay with my reversing ring. This allows me to manually focus and, more importantly set the aperture manually. To get around the lack of automatic metering the camera is set to manual exposure. With a little bit of fiddling and looking at histograms it doesn’t take long to find the right exposure.
In part two on Wednesday I’ll talk about extension rings and bellows. In the meantime post a comment below about your experiences of using either accessory lenses or reversing rings.